'Voluntary offering' in the Bible

"If his sacrifice accompanies a fulfilled vow or is a voluntary offering, it is to be eaten on the day the offeror brings the sacrifice. Anything left over is to be eaten the next day,

when you enter the land where you'll be living that I'm about to give you, you are to make an offering by fire to the LORD, either a burnt offering, a sacrificial offering to fulfill a vow, or a voluntary offering at the appointed time, to make a pleasing aroma to the LORD either from your cattle or from your flocks.

His officers contributed a voluntary offering to the people, the priests, and the descendants of Levi. Hilkiah, Zechariah, and Jehiel, the officials who supervised God's Temple, gave 2,600 animals from their flocks to the priests for Passover offerings, along with 300 bulls.

Whenever the Regent Prince presents a voluntary offering, burnt offering, or peace offering, he is to present it voluntarily to the LORD, and the east-facing gate is to be opened for him. He is to provide his burnt offering and peace offering as he does on the Sabbath. When he leaves, the gate is to be shut behind him.